1. Field of the Invention
The present invention relates to an organic thin film transistor (TFT) and a flat panel display having the same, and more particularly, to an organic TFT with reduced contact resistance between an electrode and an organic semiconductor layer.
2. Discussion of the Background
After poly-acetylene was developed, organic material-based transistors have been actively researched for use in functional electronic devices and optical devices. Generally, poly-acetylene is a conjugated organic polymer with semiconductor characteristics. It may be synthesized cheaply and in various ways, it may be easily molded in a fabric or film shape, and it is flexible and conductive.
A conventional silicon TFT has a silicon semiconductor layer with source and drain regions, which are doped with a high concentration of dopant, and a channel region between the source and drain region. A gate electrode is disposed in a region corresponding to the channel region, and it is insulated from the semiconductor layer. A source electrode and a drain electrode are coupled with the source region and the drain region, respectively.
However, conventional silicon TFTs are costly to manufacture, and they may break easily due to an external impact. Additionally, they can not be formed on a plastic substrate since the silicon is produced at a temperature above 300° C., which would damage the plastic substrate.
TFTs are typically used as switching devices that control each pixel's operation and driving devices for each pixel in flat panel display devices, such as liquid crystal displays (LCD) or electroluminescence displays (ELD). Plastic materials, instead of a conventional glass material, have been used to form a substrate in order to provide large, thin, and flexible display devices. However, since the plastic materials must be processed at a low temperature, conventional silicon TFTs can not be used.
On the other hand, this problem can be solved by using an organic film as a TFT's semiconductor layer. Therefore, research into such organic TFTs has been actively performed.
However, with the TFT having the organic semiconductor layer, high contact resistance may exist between source and drain electrodes and the organic film. The source and drain electrodes are conventionally formed of a metal having a low work function for the smooth flow of charges, but the metal can reduce the device's characteristics due to the generation of a contact resistance when it contacts the organic semiconductor layer, which can also increase power consumption.